#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>
int main() {
    double height = 0.0, sum = 0.0;
    int i = 0;
    for (i = 0; i < 5; i++)
    {
        scanf("%lf", &height);
        sum += height;
    }
    printf("%.2lf", sum / 5);
    return 0;
}